Ascully reviewed the Vantec Thermaflow Case Fans :
So what is a Thermaflow fan you ask? Well it's Vantec's answer to the thermally controlled fans companies like Enermax have been producing for quite some time now. How this works is that there is a little sensor in the middle of the fan that reads ambient heat. Depending on the temperature of your PC case, the fan will speed up or slow down, thus making the case quieter when it's cool and slightly louder when it is very hot.